It is often desired to adjust the setting or tension of the sheet secured on the winch by winding off some of the sheet. Since these sheets are under very considerable tension it is not adequate simply to release the winch and there must be some form of control of the run back. The winch works uni-directionally under usual winding, and usually it is impossible to reverse or allow reversal of the direction of rotation of the winch simply by reversing the direction of winding of the input drive.
Previous proposals for providing for controlled run back have always involved complex manually operated gear changes or releases, or manual overrides of the normal winding mechanism, the characteristic feature of all these being either that the normal input to the winch was not used and was replaced by a completely separate input or that the normal input was transferred to a completely different drive shaft system within the winch, the normal drive trains being completely disconnected.